A mobile broadband system is a wireless communication system consisting of one or more base stations deployed over a geographical region to provide wireless connectivity to subscriber stations within a coverage area of respective base stations. The mobile broadband system is based on various standards such as the Institute of Electronic and Electric Engineers (IEEE) 802.16-based WiMAX standard and its evolution to IEEE 802.16m, and typically provides various types of services such as voice, packet data and so onto subscriber stations via one or more base stations. Usually, each base station in the wireless communication network is configured to provide various types of services (e.g., voice, data, multimedia services, and the like) to subscriber stations that are operating within the geographical area served by the mobile broadband network.
In a mobile broadband system, a base station assigns an address to a subscriber station when the subscriber station performs a network entry with the base station. Typically, the base station assigns a 12 bit station identifier (STID) to subscriber stations. Sometimes, the base station may assign the same STID to multiple subscriber stations in order to support a large number of subscriber stations in a geographical area. Additionally, the base station may assign a specific time interval (e.g., frame interval) along with the STID to uniquely identify the subscriber stations to whom the same STID is assigned. Often, the base station assigns a 12-bit STID to subscriber stations for allocating resources and communicating control information with subscriber stations.
Currently, the base station assigns resources to subscriber stations through a three-step BR procedure. For example, in one three-step BR procedure, a subscriber station sends a bandwidth request to the base station on randomly selected BR opportunity requesting assignment of resources for communicating data with the base station. The bandwidth request includes a preamble sequence and a quick access message. The quick access message consists of a 12-bit STID assigned to the subscriber station and a 4-bit BR index. The base station transmits an acknowledgment in a Bandwidth Request A MAP Information Element (BR ACK A MAP IE) message upon successfully decoding the preamble sequence and the quick access message. Then, the base station transmits an uplink grant to the subscriber station as requested in the quick access message. Accordingly, the subscriber station uses the uplink grant to transmit data to the base station.
If the base station fails to decode the quick access message and successfully decodes the preamble sequence, the base station grants resources for sending a bandwidth request with STID header to the subscriber station. As a result, the subscriber station transmits a bandwidth request with STID header using the resource. The base station transmits an uplink grant to the subscriber station upon receiving the bandwidth request with STID header. Accordingly, the subscriber station uses the uplink grant to transmit data to the base station.
However, when a subscriber station, sharing a STID with other subscriber station(s), sends a preamble sequence and quick access message to the base station on a randomly selected BR opportunity, the base station fails to uniquely identify the subscriber station which has requested assignment of resources using the STID. This is because more than one subscriber station has been assigned the same STID by the base station. Although the base station has assigned a specific time interval along with the STID to uniquely identify the subscriber station from other subscriber stations sharing the same STID, a quick access message may not carry the specific time interval associated with the subscriber station due to size constraints. As a consequence, the base station may fail to assign a resource grant to the subscriber station sharing the same STID with other subscriber stations in the geographical area.